A variety of integrated circuit devices, such as operational amplifiers, require the generation of a stable bias current by a portion of the device. The bias current is used to set the magnitude of the currents used to power the various components of the device. It is very important that the bias current remain as near as possible to a predetermined level to insure that the total current required by the integrated circuit device is predictable.
A variety of forces acting upon the integrated circuit device can create fluctuations in the bias current level. Three significant forces are the ambient temperature in which the device is operating, which causes bias current fluctuations, and the variations which are introduced in the device during the construction of the device, which affect the magnitude of the bias current, and supply voltage variations.